The present invention relates generally to digital video and still cameras, and more specifically, to such digital cameras using a single-channel, solid-state imaging sensor array.
Solid-state digital video and still cameras are becoming more and more popular. Most of the current digital cameras use a single channel, solid-state photosensor array. For example, most of the digital still cameras on the market now are so-called 1-CCD (single channel charge coupled device) cameras. The solid-state photosensors are CCDs are arranged in an array in a matrix fashion with each CCD defining an element in the matrix called a xe2x80x9cpixelxe2x80x9d. By placing a mosaiced color filter over the photosensor array, a single channel image is created where each pixel has a single color component. For example for a red-green-blue (RGB) system, a pixel has a single red (R), green (G), or blue (B) color component of a full color image. This forms a single channel mosaiced color image. The single channel mosaiced color image has to be demosaiced subsequently so that a full RGB (three-channel) image is created where each pixel contains the three RGB color components.
Each single-channel digital camera has its own unique demosaicing method. A number of patents have been filed on demosaicing methods such as U.S. Pat. No. 5,552,827 granted to Maenaka et al. titled xe2x80x9cColor Video Camera with a Solid State image Sensing Devicexe2x80x9d and U.S. Pat. No. 4,716,455 granted to Ozawa et al. titled xe2x80x9cChrominance Signal Interpolation Device for a Color Cameraxe2x80x9d. However, these demosaicing methods did not take into account the filtering and sampling process performed by the optical lens and the CCD. Thus, they often generate images that are not sharp and/or have aliasing effects.
Many programs have been published and/or patented on demosaicing. However, currently, demosaicing is done in a perceptually nonuniform color space, such as RGB space. Thus, false color artifacts can appear and the picture sharpness is also limited. These have been long standing problems in the industry.
The present invention provides a demosaicing process which includes a first color transformation into a perceptually uniform color space for determining luminance and a luminance interpolation for interpolation of the missing luminance component values. The demosaicing process further includes a second color transformation for determining chrominance where the color components are known using the luminance values. A chrominance interpolation is performed to interpolate missing chrominance components and an inverse color transformation transforms the chrominance components into the RGB colors.
The present invention provides a digital camera having a lens for focusing light from an image through a RGB mosaiced filter on to a solid state photosensor array containing a matrix of CCDs. The CCDs provide a single channel mosaiced image output. A demosaicing process includes a first color transformation for determining luminance and a luminance interpolation for interpolation of the missing luminance component values. The demosaicing process further includes a second color transformation for transforming the other known color components using the luminance. A chrominance interpolation is performed to interpolate missing chrominance components and an inverse color transformation transforms the components into the RGB colors. The present invention further provides super-resolution imaging for any application involving color image data interpolation.
The present invention further provides for generating high-resolution image/video from a low-resolution one. The present invention further provides a method to interpolate an NTSC or CCIR-601 signal into a HDTV signal. The above and additional advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description when taken in conjunction with the accompanying drawings.